Pressurized steam cleaners and hot water pressure washers are utilized in a variety of situations for cleaning purposes. Such systems generally include a pump, unloading device, a burner or electrical heating elements and discharge under pressure through the trigger gun and nozzle of a wand. Equipment of this type is controlled primarily by switching the pump and heater on and then manipulating the wand as necessary to spray the object being cleaned.
A pressure washer includes an electric motor or an engine driven high pressure liquid pump. Generally, the pump has a water inlet which is connected through a hose to a water main. Optionally, a suitable cleaning solution may be mixed with the water either at the pump or upstream or downstream from the pump. The pump increases pressure of the water or other liquid from a relative low inlet pressure to a significantly higher outlet pressure. The high pressure water is delivered to a wand for directing a water spray at a surface to be cleaned. Normally, the wand includes a manually operated trigger valve for turning the water flow on and off, and a nozzle which shapes the spray pattern and determines the velocity of the high pressure spray. When the valve is closed, the pump can be subjected to a high static load. An unloader valve may be provided for allowing the pump to continue to operate by recirculating the water through the unloader valve back to the inlet to the pump. However, a typical unloader valve may still place a sufficient back load on the pump to cause excess heat buildup and excess wear on the motor and pump. When the pump is driven by an electric motor, a pressure responsive switch may be provided to shutdown the pump and motor either directly or via a timer when the water discharge valve (trigger gun) is closed to prevent excess wear on the motor and pump, excess heat generation and unnecessary energy consumption.
While these methodologies exist to protect the engine/motor and pump, they do not address the high temperature and high pressure water trapped between the unloader and trigger gun. The burner heating coil may still be at 800° F. and continues to transfer thermal energy to the trapped water inside the coil. This energy transfer results in a temperature rise of the trapped water and a corresponding pressure increase in the trapped body of water. This increase in temperature and pressure serves to damage components and shorten their life expectancy. Currently there is no existing art to relieve the high pressure trapped between the unloader and trigger gun, nor cool down the burner heating coil.
It is an object of the present invention to introduce an apparatus for steam cleaning and hot water pressure washing that comprise a control safety circuit for the steam cleaner and/or hot water pressure washer which incorporates predetermined automatic depressurization and cool down of the heating coil.